APBIO muscle contractionDescribe how the muscle contraction works by using sliding theory in a molecular level. You must specifically explain how...

The “Sliding-Filament Theory of Muscle Action”
explains how the movement of thick and thin filaments relative to each other leads
to the contraction and relaxation of whole muscles. There are two physical units that are
important for the action of muscles: thick filament and thin
filaments. Muscle tissues can be described in terms of units called
sacromere. These units are defined in terms of groups of overlapping
filaments (thick and thin filaments). The length of a sacromere and the zones
within each sacromere (H zone, I band, and A band) are determined by the positions
of the thick and thin filaments relative to each other. This sliding filament
mechanism can only occur when there are sufficient calcium ions and
ATP.

During Muscle Contraction, the
myosin heads on the thick filaments "hook" onto, and so pull, the
thin filaments towards the centre, which is "M-line", of each
sacromere. As the thin filaments slide over the thick filaments, the I bands and H zones becomes
narrower and narrower until they disappear when the muscle reaches its fully contracted
state.

During Muscle Relaxation, the
myosin heads release their hold on the thin filaments when the myosin heads on the thick
filaments relax, thereby allowing them to slide back to their "relaxed" positions in which the I
bands and H zones appear again.

This leads to questions about what
causes the myosin heads to lock onto the thin filaments and pull them, and what causes them to
relax and release their hold on the thin filaments. These processes happen as a result of
instructions sent via the nervous system to activate and deactivate these tissues. The muscular
and nervous systems are connected to each other by neuromuscular
junctions.